essential to plant growth and is a fertilizer, but it is 

 not sufficiently concentrated to pay for handling and 

 transportation. 



Each of the three plant foods, nitrogen, phos- 

 phoric acid and potash, have their respective market 

 values for each 1 per cent., or unit, of 20 pounds to 

 the ton. If a ton of fertilizer contains 3 per cent, pot- 

 ash, that means 60 pounds. The purchaser will have 

 to know the market value and the source of the 

 nitrogen, phosphoric acid and potash before he can 

 determine the value of a ton of a certain analysis. 

 The source is very important, because the most avail- 

 able forms have the highest market value. Without 

 this knowledge, a certain brand may sell for $40 a 

 ton and another worth only one-half its value ($20 

 per ton) may sell more readily for $38. 



Each of the three essential plant foods has its 

 special part to do in the building of the plant. One 

 cannot do the work of the other. As an illustration : 

 Nitrogen in the absence of potash may produce a 

 luxuriant and rapid growth but it will be weak and 

 broken down by the first wind ; add potasli and that 

 same succulent, weak growth will be matured and 

 have strength enough to carry its load of fruit. 

 Potash alone will not produce the growth, but will 

 mature it. Both nitrogen and potash have many 

 other functions to perform. 



Phosphoric acid, or phosphorus, must be present 

 7 



